US9302931B2 - Glass ceramic article and method and device for ceramizing glass - Google Patents

Glass ceramic article and method and device for ceramizing glass Download PDF

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Publication number
US9302931B2
US9302931B2 US13/262,284 US201013262284A US9302931B2 US 9302931 B2 US9302931 B2 US 9302931B2 US 201013262284 A US201013262284 A US 201013262284A US 9302931 B2 US9302931 B2 US 9302931B2
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glass
green glass
temperature
roller
ceramized
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US20120094079A1 (en
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Falk Gabel
Thoralf Johansson
Uwe Martens
Christian Roos
Friedrich Georg Schroder
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Schott AG
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Schott AG
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    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B29/00—Reheating glass products for softening or fusing their surfaces; Fire-polishing; Fusing of margins
    • C03B29/04—Reheating glass products for softening or fusing their surfaces; Fire-polishing; Fusing of margins in a continuous way
    • C03B29/06—Reheating glass products for softening or fusing their surfaces; Fire-polishing; Fusing of margins in a continuous way with horizontal displacement of the products
    • C03B29/08—Glass sheets
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B32/00—Thermal after-treatment of glass products not provided for in groups C03B19/00, C03B25/00 - C03B31/00 or C03B37/00, e.g. crystallisation, eliminating gas inclusions or other impurities; Hot-pressing vitrified, non-porous, shaped glass products
    • C03B32/02—Thermal crystallisation, e.g. for crystallising glass bodies into glass-ceramic articles
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B35/00—Transporting of glass products during their manufacture, e.g. hot glass lenses, prisms
    • C03B35/14—Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands
    • C03B35/16—Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands by roller conveyors
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B35/00—Transporting of glass products during their manufacture, e.g. hot glass lenses, prisms
    • C03B35/14—Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands
    • C03B35/16—Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands by roller conveyors
    • C03B35/18—Construction of the conveyor rollers ; Materials, coatings or coverings thereof
    • C03B35/181—Materials, coatings, loose coverings or sleeves thereof
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
    • C03C10/0018—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and monovalent metal oxide as main constituents
    • C03C10/0027—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and monovalent metal oxide as main constituents containing SiO2, Al2O3, Li2O as main constituents
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
    • Y10T428/24479—Structurally defined web or sheet [e.g., overall dimension, etc.] including variation in thickness
    • Y10T428/24488—Differential nonuniformity at margin

Definitions

  • the invention relates to a method and a device for ceramizing green glass and to glass ceramic products that can be produced using the method.
  • the invention relates to a method and a device that allow green glass to be ceramized directly on the rollers of a conveying system and to the products that can be produced using this method and the device.
  • U.S. Patent Application No. 2005/016214 A1 teaches a continuous method for producing crystallized glass plates and a device for carrying out the method. This method comprises the steps of melting a crystallizable glass material, adjusting the viscosity of the molten material, rolling the glass between rollers and/or cylinders to form a glass ribbon, and passing the glass ribbon through a crystallization tunnel in which the glass ribbon is crystallized.
  • the glass ribbon is transported in the crystallization tunnel on a conveyor that is composed of rollers made of a heat-resistant material.
  • a “pressing roller” is optionally provided upstream of the entrance into the crystallization tunnel and presses the freshly formed glass ribbon against the conveyor so as to obtain a planar ribbon.
  • the cited document does not contain any information on many key parameters, for example, the total duration of the ceramization process, the maximum temperatures during ceramization and related viscosities of the glass ribbon, or the distances between the individual rollers of the conveyor.
  • this information is essential in order to be able to produce glass ceramic articles having sufficient flatness.
  • the glass ribbon has very low viscosities, which cause the glass ribbon to “sag” between the rollers if the distances are too great, thus causing the ceramized product to exhibit strong waviness. It would therefore be desirable to be able to control the method so that the period of the lowest viscosity, which is reached, in general, just prior to and at the start of volume crystallization, is passed in the shortest time possible.
  • this is difficult because short periods of high viscosity are gained by ceramization temperatures that, at least intermittently, are very high, which in turn make the exothermal process of ceramizing difficult to control.
  • short ceramizing times also result in lower minimal viscosities of the ceramizing green glass, making it more difficult to handle because it deforms more easily.
  • Transporting the green glass on support plates has the disadvantage that the side of the green glass that rests on the support plate has only limited contact with the furnace atmosphere, resulting in differences between the upper face and lower face of the ceramic article that is produced with respect to the properties thereof, for example, mechanical strength, chemical resistance, transparency and the like.
  • the support plates must be preheated every time they are used and they also must be continuously heated during ceramization, which leads to significant added energy expenditure and is also more time-consuming because additional process steps are required.
  • direct ceramizing of the green glass on rollers has the advantage that considerably less material required exclusively for conveying the green glass must be heated as well.
  • the method according to the invention accordingly provides for the ceramization of green glass, with the green glass being conveyed and/or supported directly on rollers, at least during volume crystallization.
  • the method can be carried out at a high ceramization rate that allows at least one region of the green glass, after the forming operation has been completed for this region, to be ceramized in a process that includes ceramization all the way to completion of the cooling step of the ceramized region within only 0.5 to 4 hours.
  • the period in which the green glass is exposed to maximum temperatures during volume crystallization comprises only 5 to 60 minutes, with the maximum temperatures ranging between 750 and 1250° C. This further increases the energy efficiency that is achieved by processing without a support plate.
  • the method is continuous in that the ceramization is carried out while the product passes through the furnace.
  • the invention can, in general, be employed for both the ceramization of individual plates and for a continuous ribbon. Accordingly, in particular green glass in the form of a continuous green glass ribbon is, or individual green glass plates, are used as the starting substrate. In the case of a green glass ribbon, the ceramization is preferably followed by a singulation or a separation into individual plates.
  • a green glass as defined by the invention is generally a starting substrate which is converted into a glass ceramic material that is structurally different from the material of the starting substrate by means of ceramizing using the method according to the invention.
  • This glass is preferably an amorphous glass.
  • the green glass can also already contain crystal phases.
  • the use of the invention on glass ceramics as the starting substrates, or green glass, and carrying out a ceramization in the form of a recrystallization has been considered.
  • the transformation of a high-quartz mixed-crystal phase of the starting substrate into a keatite mixed-crystal phase shall be mentioned as an example here.
  • the temperatures of the upper and lower faces of the ceramizing segment of the green glass are continuously measured and the heating is controlled using this information based on target values.
  • the viscosity of the green glass to be ceramized can range, at least intermittently, between 10 7 and 10 11 dPa ⁇ s. Given this low viscosity, the conveying device is subject to high requirements for the conveyance, at least during the time segment in which the viscosity reaches minimum values. If too far a distance between rollers is selected, the advancing rate is too low or the temperature too high, the glass ribbon to be ceramized, or the plate to be ceramized, can “sag” between the supporting rollers, resulting in undesirable waviness of the end product. In extreme cases, it is even possible for the glass ribbon to break between individual rollers, which would disrupt the entire continuous production process.
  • the distance between the rollers of the conveying device is therefore a function of the advancing rate of the glass ribbon and the temperature at this time, which in turn determines the lowest viscosity of the green glass just prior to the start of volume crystallization.
  • the advancing rate of the glass ribbon should range between 0.2 and 10 m/min., preferably between 0.5 and 5 m/min., at the lowest viscosities of 10 7 to 10 11 Pa ⁇ s. Rapid advancing rates lower the risk that the low-viscosity material may sag.
  • the distance X Roller between the roller axes can also be estimated using the formula x Roller 5 ⁇ 360*( R a *t Pane 2 )/( ⁇ * g )* v* ⁇ where R a is the maximum glass deflection, t Pane is the glass thickness, ⁇ the glass density, g the acceleration due to gravity, v the advancing rate and ⁇ the minimum viscosity of the glass over the course of ceramization on the rollers.
  • this relationship can be used to determine the maximum roller distance as a function of the advancing rate and the minimum viscosity that is reached during ceramizing.
  • the relationship can also be maintained by appropriately controlling at least one of the parameters consisting of the advancing rate or temperature, or minimum viscosity of the glass.
  • the measuring and control unit is equipped to control the temperature and/or the advancing rate so that the above relationship is met. Good values for R a are below 100 micrometers, as will be described in more detail hereafter.
  • a pressing roller as is known from U.S. Patent Application No. 2005/016214 can also be omitted without resulting in increased waviness.
  • the method according to the invention has several advantages over the prior art.
  • this type of ceramization is fundamentally suited for converting glass ribbons having infinite lengths and widths.
  • the glass ribbon length and width are solely limited by the existing technical options, such as the available installations and the components thereof (heating elements, roller lengths, and the like).
  • the ceramization is not carried out on support plates but rather on a roller system.
  • the energy-intensive heating of the support plates which is used exclusively for conveying the green glass and is incurred anew each time the plates are introduced into the furnace, is not necessary.
  • a roller system is fixedly installed and must be heated only once when heating the furnace. Subsequently, only the energy that is required to maintain the temperature of the heated rollers must be supplied. In total, at least 50% by weight of the mass that must be heated to ceramization temperatures during ceramizing is thus saved, which entails considerable time savings, and notably cost savings.
  • the method according to the invention also exhibits clear advantages over ceramizing on a bath of molten metal, for example, a float bath made of tin.
  • a bath of molten metal for example, a float bath made of tin.
  • no special atmosphere is required during ceramizing, which entails considerable cost advantages.
  • contamination of the side of the green glass that rests on the float bath is avoided.
  • such a contamination can result in ceramization that is difficult to control, or can no longer be controlled at all, because the crystallization process takes place exothermically. Supporting the green glass on a float bath would thus be associated with great difficulties, at least with respect to process control, or would make such control even impossible, with fast ceramization.
  • the rollers of the conveying device are disposed at a distance from one another so that, at a predefined advancing rate and a viscosity of the region of the green glass to be ceramized that is induced by the prevailing temperatures and the degree of ceramization, only minor waviness of the product develops.
  • This minor waviness is no more than 100 ⁇ m, preferably even no more than 50 ⁇ m, measured as the difference in height between a wave valley and an adjoining wave peak, the waviness being periodic and having a preferred direction.
  • the preferred direction is determined by the running direction of the plate, or the ribbon, on the rollers.
  • Waviness that is only minor and preferably imperceptible or almost imperceptible to the eye allows the products that are produced using this method to be employed in fields which require a planar surface, which is to say, for example, as a window, façade panel or glass ceramic cooktop. Products thus produced are generally suited as replacements for ceramics and high-performance ceramics. High-performance ceramics are employed wherever the requirements are high for at least one of the factors consisting of thermal loading, wear resistance, thermal shock resistance and electric insulation capability. Fields of use include bearing elements, sealing elements, piston and valve elements, nozzles, and stamping and molding tools.
  • waviness that is clearly perceptible to the eye is composed of two parameters.
  • the amplitude as described above, is decisive.
  • the visibility of this amplitude is directly related to the wavelength of the waviness.
  • Waviness that is visible to the eye exists, for example, at amplitudes greater than 50 ⁇ m in conjunction with wavelengths of less than 135 mm. Such waviness is no longer acceptable if flat articles are required.
  • a minimum waviness at which the difference in height between a wave valley and an adjoining wave peak is at least 1 ⁇ m, preferably at least 5 ⁇ m, generally facilitates the handling of the articles produced, in particular if larger plates are involved.
  • Glass ceramic articles in general, respond with great sensitivity to any damage to the surfaces thereof, which leads to losses in the mechanical properties, such as the strength thereof, but also lower the chemical resistance thereof.
  • Minor waviness in particular if the waviness has a preferred direction as is the case according to the invention, limits the surface area and thus the regions that can become scratched when the article is handled carelessly, during packaging, for example.
  • glass ceramic plates can be stacked on top of one another so that only point contacts exist between the individual plates due to the preferred direction of the minimum waviness. The risk of the glass ceramic plates becoming scratched is thus considerably reduced.
  • Periodic waviness should be understood as several wave valleys, each followed by a wave peak, following one another. A wave peak and a subsequent wave valley are thus considered to be a cycle.
  • periodic thus means, in the broadest sense, “cyclic;” the cyclicity need not be regular.
  • the waviness spacing of an article preferably does not deviate from an average value by more than 30%.
  • a preferred direction in the waviness describes the fact that long-drawn wave crests and long-drawn wave valleys form.
  • the term preferred direction is used within the context of the present invention primarily to highlight a contrast to large-surface-area elevations or indentations that have no preferred direction and can run over the entire glass ceramic article. These individual structures, which may encompass the entire glass ceramic article, are not excluded according to the invention. However, they are superimposed with the considerably shorter-spaced periodic waviness.
  • the wavelengths of the waviness range between 50 and 500 mm, preferably between 60 and 200 mm.
  • this method can also be employed to produce pebbled surfaces.
  • the surface structuring is then carried out during, or immediately following, the forming process of the green glass.
  • pebbled surfaces are frequently generated exclusively in order to locally limit damaging and moisture-reducing influences to the pebble tips. These damaging influences thus almost never achieve a critical level, which is to say the strength property of the glass ceramic is not negatively influenced, as long as the damage only affects the pebble tips.
  • Undesired deformations of the ceramizing green glass can primarily be attributed to temperature gradients in the vertical direction.
  • pebbled surfaces can also be produced using the method according to the invention.
  • the method according to the invention can be used to produce transparent, translucent, uncolored and volume-colored, as well as opaque glass ceramic articles.
  • Transparent glass ceramic articles are generally characterized by a main crystal phase made of high-quartz mixed crystals
  • translucent to opaque glass ceramics are generally characterized by a main crystal phase made of keatite mixed crystals.
  • a main crystal phase shall be understood to mean a crystal content of at least 60% in the total crystal content.
  • the generation of a flat or planar surface is supported by as high a temperature homogeneity as possible within the green glass ribbon to be ceramized.
  • the temperature over the width of the green glass T y to be ceramized in the furnace does not deviate by more than ⁇ 5° C. to +5° C. from a predefined target temperature T.
  • the temperature difference over the width of the green glass to be ceramized in the furnace is less than 10° C., preferably less than 5° C., and still more preferably less than 3° C.
  • the temperature homogeneity between the upper and lower faces of the green glass to be ceramized is also controlled so that the temperature difference between the upper and lower faces of the glass in the furnace ranges between ⁇ 0.5° C. and +1° C.
  • This control is important, in particular, with respect to the flattest or most planar generation possible of the ceramized article and to avoid ceramization stress because varying temperatures can result in varying volume expansions of the hot material.
  • varying volume expansions again favor disadvantageous or even unacceptable buckling of the plates, such as upward arching of the corners thereof or buckling of the center region thereof, for example.
  • a device for carrying out the method provides for a measuring and control apparatus that controls the temperature adjustment based on current measurement values and target specifications.
  • the measuring and control apparatus is generally able to respond to changed conditions within 10 seconds, and in the most favorable cases even within one second.
  • Such a measuring and control apparatus can be composed, for example, of temperature sensors connected to a computer and a temperature control apparatus also connected to the computer.
  • the heating device which generates a very homogeneous heat distribution, can be composed, for example, of heating elements known to a person skilled in the art disposed at regular intervals relative to one another that preferably project at least 10 cm beyond the edges of the green glass to be ceramized.
  • the projection of the heating elements beyond the edges of the green glass is useful so as to also achieve homogeneous temperature distribution in the edge region of the green glass.
  • the green glass to be ceramized and/or the ceramized product has a composition in the following range:
  • the method can be applied to a broad range of compositions. It is also possible, for example, to produce glass ceramic composition from remelt phases. Here, components of the composition range described above can also be entirely absent.
  • the volume crystallization and an optional maturing phase at a maximum temperature are followed by fast cooling to below 600° C., with the cooling rate being at least 5° C./min., preferably between 10 and 20° C./min., at least intermittently.
  • the interaction with the atmosphere prevailing in the furnace during volume crystallization or ceramization can take place without local restrictions and in a completely unimpaired fashion in the method outlined so far.
  • the thickness of the vitreous layer, or of the vitreous edge region typically ranges between 50 and 5000 nanometers, in most instances between 250 and 3000, and preferably between 300 and 1500 nanometers.
  • the substantially vitreous edge region comprises no more than 10% by weight of crystals, which is to say at least 90% by weight of the edge region is made of a vitreous matrix.
  • the vitreous edge region still more preferably comprises less than 1% by weight of crystals.
  • the content of crystals in the substantially crystalline inside region of the glass ceramic article is at least 50% by weight, preferably at least 80% by weight, and still more preferably at least 90% by weight.
  • the detection method employed here is X-ray diffractometry.
  • vitreous edge region increases the light transmission or transparency by up to 1%, in absolute terms, compared to a glass ceramic article that has no vitreous edge region.
  • translucent or opaque glass ceramics benefit from the generation of a vitreous layer by having improved mechanical strength and chemical resistance.
  • the roller surfaces preferably contain at least one of the materials comprising silicon carbide, silicon oxide, corundum or mixtures of the system of fused/sintered mullite-sillimantin, boron carbide and boron nitride. These materials have sufficient heat stability, and glass ceramics produced on such rollers exhibit surprisingly similar damage-free and defect-free surfaces as glass ceramics of the same type that were produced on support plates, the surfaces of which were specially conditioned for this purpose.
  • a ratio between the roller diameter d Roller and roller length l Roller of 0.25 ⁇ d Roller /l Roller ⁇ 0.9 should be maintained. It is particularly preferred for this ratio to be 0.5.
  • the green glass plates are applied or placed obliquely on the conveying apparatus, which is to say the rollers, when ceramizing individual green glass plates, so that one of the corners leads the remaining plate.
  • the starting or end region of a plate that is not supported by rollers and has decreased viscosity can be reduced as compared to a “straight” conventional arrangement of the plate.
  • This also reduces the unsupported weight component of the plate during the transition between two adjoining rollers.
  • This arrangement is intended to help prevent the front edge of the plate in the advancing direction, which may droop due to the decreased viscosity and the unsupported dead weight, from striking against the subsequent roller and becoming damaged and deformed in the process.
  • the end region of the plate undergoes less downward bending, because the unsupported mass during the transition between two plates is reduced here as well.
  • a device for carrying out the method according to the invention preferably comprises an apparatus that provides the green glass to be ceramized.
  • This is, in particular, a device for melting and forming the green glass, which is connected directly upstream of the ceramizing device according to the invention. It is also possible, however, for a suitable feeding system to continuously supply previously singulated green glass plates.
  • a continuous furnace for ceramizing the green glass, with the continuous furnace being equipped to carry out the entire ceramization process within 0.5 to 4 hours.
  • At least one chamber of the continuous furnace is equipped for volume crystallization of the green glass and comprises apparatuses that allow separate heating of an upper face and a lower face of the green glass to be ceramized to 750 to 1250° C.
  • this region of the furnace comprises a measuring and control apparatus, which can not only assume the control of the entire device, but above all is also equipped to detect temperature changes on the upper and lower faces of the ceramizing green glass within just a few seconds and to adapt the temperature adjustment of the furnace accordingly, which in the most favorable case is done within one second. This fast response time is necessary to ensure effective control over the exothermic ceramization process.
  • the continuous furnace additionally comprises a conveying apparatus, which comprises rollers for conveying and/or supporting the green glass, at least in the furnace region in which volume crystallization takes place; an advancing rate of between 0.2 and 10 m/min., and preferably between 0.5 and 5 m/min., can be implemented.
  • a conveying apparatus which comprises rollers for conveying and/or supporting the green glass, at least in the furnace region in which volume crystallization takes place; an advancing rate of between 0.2 and 10 m/min., and preferably between 0.5 and 5 m/min., can be implemented.
  • the roller axes are disposed from each other at a distance of at least the diameter of the rollers plus 0.2 cm and of no more than the diameter of the rollers plus 10 cm, at least in the region in which volume crystallization or ceramization takes place. This enables a good temperature exchange on the lower faces of the plates, and thus also good control of the temperature.
  • the conveying unit thus comprises rollers that are disposed at variable or aperiodic distances, with the distances and the diameters of the rollers being dimensioned so as to prevent “sagging” of the green glass ribbon to be ceramized.
  • rollers can also be disposed such that the distances between rollers do not repeat at regular intervals.
  • the advancing rate can be increased during ceramization.
  • the rollers can run, or be driven, successively faster along the advancing direction.
  • the accelerated advancement effects a drawing of the plate, thus preventing or correcting the sagging of the plate between the rollers.
  • Glass ceramic articles that can be produced by means of the method according to the invention can be used as panes, in particular vehicle windows, fireplace windows or cooktops, as cookware in general, or for façade claddings. However, they can, in general, also be used as replacements for high-performance ceramics.
  • FIG. 1 a is a schematic view of a typical device by which the method according to the invention can be carried out
  • FIG. 1 b shows a typical temperature-time profile of a method according to the invention
  • FIGS. 2 a, b shows the deformation in three different locations of a ceramizing plate during conveyance over a roller system with non-varying viscosity
  • FIG. 3 shows the influence of various minimum viscosities directly prior to and at the start of volume crystallization on the deformation of a ceramized article
  • FIG. 4 shows the waviness of a ceramizing green glass plate as a function of the roller distance, plotted in relation to the longitudinal plate position,
  • FIG. 5 shows the effects of periodic and aperiodic roller distances on the waviness of the glass ceramic article
  • FIG. 6 shows the influence of the advancing rate on the deformation of the glass ceramic article
  • FIG. 7 shows the influence of an accelerated advancement on the deformation of the glass ceramic article
  • FIG. 8 shows the influence of the length of the green glass to be ceramized on the waviness of the ceramized article.
  • FIG. 1 a schematically shows a typical device 1
  • FIG. 1 b shows a related typical, exemplary temperature-time profile 10 , by means of which a ceramization method according to the invention can be carried out.
  • the method according to the invention for continuously ceramizing green glass 2 is characterized by ceramization directly on a roller conveying system 3 , with very short ceramization durations of only 0.5 to 4 hours being provided for.
  • Such a combination for the production of high-quality products is only possible if the parameters that influence the flatness of the product are determined within a very precise range and, in particular, are tailored to one another.
  • the temperature adjustment for example, decisively influences the viscosity of the ceramizing green glass 2 .
  • FIG. 1 a schematically shows a typical device 1
  • FIG. 1 b shows a related typical, exemplary temperature-time profile 10 , by means of which a ceramization method according to the invention can be carried out.
  • the method according to the invention for continuously ceramizing green glass 2 is
  • thermocouples 8 project into the furnace in order to control the temperature.
  • Thermocouples are disposed both above and below the green glass in order to produce the lowest temperature difference possible between the upper and lower faces of the green glass.
  • the viscosity determines how large the gaps between the individual rollers 4 of the conveying system 3 can be, so that the low-viscosity green glass 2 does not sag between the individual rollers 4 and no undesirable waviness is generated in the end product.
  • the roller-type furnace 1 shown in FIG. 1 a is only intended as a possible example of a device by which the method according to the invention can be carried out, which within the proper meaning refers only to the period directly prior to volume crystallization and the period of volume crystallization as such.
  • nucleation takes place in one or more chambers 5
  • volume crystallization takes place in two to three chambers 6
  • four to six chambers 7 are used for cooling the ceramized green glass 2 at the end of the method.
  • the temperature-time profile 10 shown in FIG. 1 b is likewise only intended as a schematic example, for which reason no absolute values are indicated.
  • the temperature 11 and time 12 are to be understood to be a function of a special method, which is not the topic of this application, but is only incorporated herein in the form of limiting framework parameters, such as the total time or maximum temperatures.
  • the individual phases of a typical ceramization program are shown, which is to say nucleation 13 , volume crystallization 14 , maturing phase 15 and cooling 16 .
  • the heating phase at the beginning of the process is generally not required if a glass ribbon is ceramized immediately following the hot-forming process and if sufficient residual heat is present.
  • FIGS. 2 a and 2 b show the deformation (deviation from a starting value) of a ceramizing green glass ribbon 2 in the shape of a long pane that is conveyed by a roller system 3 , shown as a function of the time t in seconds.
  • the deformation V is indicated in millimeters.
  • the deformation in relation to the time is shown based on three points selected by way of example. Point 1 denotes a location at the start of the plate, point 2 denotes a location at the end of the plate, and point 3 denotes a location in the center of the plate.
  • the conveyed pane is 5 m long and 4 mm thick.
  • the viscosity of the ribbon is approximately 10 9 Pa ⁇ s and does not change over time.
  • the rollers of the conveying system have a diameter of 5 cm and are disposed at regular intervals between the roller centers of 10 cm.
  • the advancing rate is 60 cm/min.
  • curves 21 , 22 and 23 in FIGS. 2 a and 2 b depict the deformation of three exemplary points on a glass ribbon in relation to the time.
  • curve 21 in FIG. 2 a and curve 23 in FIG. 2 b show only the envelopes of the oscillating lines.
  • FIG. 2 a shows the envelope 21 of the movement curve of a point that is located at the front, or at the start of the plate, in the conveying direction of the ribbon.
  • the envelope 21 After approximately 200 seconds, the envelope 21 exhibits a maximum amplitude, which then slightly decreases again toward the end of the period. On an overall basis, after approximately half the time, a tendency can be observed toward an upward movement of this center region of the ribbon, so that this region of the ribbon again has a lower degree of waviness after 400 seconds.
  • the curve 22 in FIG. 2 b shows a detailed plotting of the movement of a point located in the center of the ribbon, with each upward trend of the curve 22 corresponding to the rolling of this point onto a roller 3 , and each downward trend denoting the movement of the ribbon in the location of the point between two adjoining rollers.
  • the downward trend thus traces how the ribbon moves downward when “rolling off” a roller on the path to the adjoining roller due to the low viscosity and the force of gravity.
  • the upper and lower envelopes of the curve 22 are each shown as dotted lines.
  • the envelope of the curve 22 shows that the amplitude of the center part of the ribbon is 50 ⁇ m after 400 seconds, which is to say that, under these conditions, the ribbon has a maximum difference in height from a wave peak to an adjoining wave valley of 50 ⁇ m.
  • FIG. 2 b moreover shows the envelope 23 of the movement curve of point 2 , which is to say that a point that is located at the back in the movement direction of the ribbon. Again, for the benefit of clarity, a detailed view of the entire curve progression has been omitted.
  • the envelope 23 shows a steady rise in the amplitude, and thus in the waviness, at the rear end of the ribbon over the course of time. Toward the end of the period shown, however, the progression of the envelope increasingly approaches a constant progression.
  • the maximum difference in height between a wave peak and an adjoining wave valley is approximately 450 ⁇ m at the end of the glass ribbon under the aforementioned conditions.
  • FIG. 3 shows the influence of varying minimum viscosities directly prior to and at the start of volume crystallization on the deformation of a ceramized article.
  • the graph shows the deformation of the article on the y-axis as a function of the plate length, which is plotted along the x-axis.
  • the unit of both the x-axis and of the y-axis is millimeters. Zero millimeters on the x-axis correspond to the rear end of the plate in the conveying direction, 1000 mm corresponds to the front edge of the plate, as viewed in the conveying direction.
  • the curves 33 , 34 , 35 and 36 show identical plates that were ceramized under identical conditions, with only the viscosities being different.
  • the plate length is 1 m
  • the plate thickness is 4 mm
  • the roller diameter 50 mm the roller distance 100 mm
  • the advancing rate is 60 cm/min.
  • the viscosities of the plates shown in the curves are as follows:
  • Curve 33 10 9.6 Pa ⁇ s Curve 34 10 9.4 Pa ⁇ s Curve 35 10 9.2 Pa ⁇ s Curve 36 10 9.0 Pa ⁇ s.
  • the deformation curves 33 , 34 , 35 , 36 show that, with otherwise identical parameters, the deformation increases the lower the viscosity of the green glass during the phase of the lowest viscosity.
  • FIG. 4 shows the waviness of a ceramizing green glass plate 2 as a function of the roller distance, plotted in relation to the plate length.
  • the roller distance refers to the distance between the roller centers of adjoining rollers.
  • the ceramized plate is 1 m long, 4 mm thick and has a viscosity of 10 9.0 Pa ⁇ s.
  • the deformation of the plate is plotted on the y-axis, and the plate length is plotted along the x-axis, both in millimeters. All examples were conveyed on conveying systems having a regular or periodic roller distance. The roller distance is 50 mm in all examples.
  • the curve 43 depicts the deformation of a ceramized plate that was conveyed on a conveying device 3 in which the roller distance is 75 mm.
  • the curve 44 depicts the deformation of a ceramized plate that is generated at roller distances of 100 mm, while the curve 45 depicts the deformation that is generated at roller distances of 125 mm.
  • R a /R a1 ( x Roller /x Roller1 ) 5 *( ⁇ / ⁇ 1 ), where R a is the quadratic mean of the deviation from an average value and denotes the average waviness in micrometers, x Roller denotes the distance between adjoining roller centers and ⁇ denotes the viscosity.
  • the additional index 1 denotes the same parameters, albeit at a different roller distance.
  • a roller distance of 75 mm result in an average waviness of 5.28 ⁇ m
  • a roller distance of 100 mm results in a waviness of 22.64 ⁇ m
  • a roller distance of 125 mm results in a waviness of 73.03 ⁇ m.
  • the spacing appears to scale at a factor of 1.1 to 1.3 to the roller distance.
  • FIG. 5 shows the effects of periodic and aperiodic roller distances on the deformation of the glass ceramic article.
  • the y-axis shows the deformation V and the x-axis shows the length s of the plate, both in millimeters.
  • the same values as in FIG. 3 apply to the plate length, plate thickness, viscosity and roller diameter.
  • the curve 51 depicts the deformation of the plate that was ceramized on a conveying system having regular roller distances of 100 mm.
  • the curve 52 depicts the deformation of the same plate, which was ceramized on a conveying system having irregular roller distances.
  • the roller distances were alternately 80 and 120 mm, so that pairs form that are positioned closely together and separated from each by a larger gap.
  • the waviness is reduced by approximately 2 ⁇ m due to rollers that are disposed at varying distances (curve 52 ).
  • the wavelength in the front region of the glass plate appears to be longer with aperiodic roller distances (curve 52 ) than with periodic roller distances (curve 51 ).
  • the spacings conform to one another again in the rear region.
  • FIG. 6 shows the influence of the advancing rate on the deformation V of the glass ceramic article.
  • the deformation is again plotted in relation to the plate length s, both in millimeters.
  • the size of the plate, the viscosity and the roller diameter again correspond to the values provided for FIG. 3 .
  • the roller distance is 100 mm.
  • the three curves 61 , 62 , 63 shown differ from one another in the advancing rate at which the plates were conveyed during ceramization.
  • the plate represented by the curve 61 was conveyed at 30 cm/min.
  • the plate represented by the curve 62 at 60 cm/min.
  • the plate conveyed the fastest has the least deformation (curve 63 ).
  • the relationship between the average waviness and the advancing rate is approximately linear and is derived from the following equation: R a /R a1 ⁇ ( v Advancement /( v Advancement1 + ⁇ v Advancement1 ))*( ⁇ / ⁇ 1 ), where R a again corresponds to the average waviness, ⁇ to the viscosity and v Advancement to the advancing rate.
  • the additional index 1 denotes the same parameters, albeit for different advancing rates.
  • FIG. 7 shows the influence that an accelerated advancement during ceramization has on the deformation of the known glass ceramic article.
  • the deformation V of the plate is shown on the y-axis in millimeters, and the plate length 18 is shown along the x-axis, likewise in millimeters.
  • the curve 71 shows the deformation of a plate that was ceramized at a constant advancing rate of 60 cm/min.
  • the curve 72 shows the deformation of a plate that was ceramized at an increasing advancing rate.
  • the advancing rate is a constant 60 cm/min. over the first meter of the 5-meter-long conveying device. Over the remaining 4 m, the advancing rate increases continuously to 120 cm/min. The plate is thus uniformly accelerated.
  • the comparison of the deformation curves 71 and 72 shows that an acceleration of the advancement reduces the deformation of the plate, in particular with respect to the amplitude. However, the acceleration of the advancement appears to have little or no influence on the spacing of the deformation.
  • FIG. 8 depicts the influence of the length of the green glass to be ceramized on the waviness of the ceramized article. Apart from the length of the plates 18 , all parameters such as plate thickness, roller distance, roller diameter, viscosity and advancing rate are identical to and correspond to the values indicated in the description of FIG. 3 .
  • the deformation of the article is shown along the longitudinal axis.
  • the curve 81 shows the deformation of a plate 1 m long
  • the curve 82 shows that of a plate 2 m long.
  • the thickness of the ceramizing article decisively influences the waviness that can be achieved. It goes without saying that, at low viscosities, thicker plates deform less easily than thin plates. The plate or ribbon thickness has no effect on the spacing of the deformation, only on the amplitude.
  • the additional index 1 denotes the same parameters, albeit for different pane thicknesses.
  • a formula can be derived from the different influencing factors described above that takes into account the different influencing factors on the waviness.
  • the additional index 1 denotes the same parameters, albeit as a function of a changed parameter.

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  • Crystallography & Structural Chemistry (AREA)
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  • General Chemical & Material Sciences (AREA)
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US13/262,284 2009-03-31 2010-03-20 Glass ceramic article and method and device for ceramizing glass Expired - Fee Related US9302931B2 (en)

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DE102009015089 2009-03-31
DE10-2009-015089.31 2009-03-31
DE102009015089A DE102009015089B4 (de) 2009-03-31 2009-03-31 Verfahren und Vorrichtung zur Keramisierung von Gläsern, Glaskeramikartikel und seine Verwendung
PCT/EP2010/001766 WO2010112148A1 (de) 2009-03-31 2010-03-20 Glaskeramik-artikel, sowie verfahren und vorrichtung zur keramisierung von gläsern

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DE102010017087B4 (de) * 2010-05-26 2013-08-22 Schott Ag Feuerstätte
JP2012240857A (ja) * 2011-05-16 2012-12-10 Huzhou Daikyo Hari Seihin Yugenkoshi 結晶化ガラスの連続成形方法および結晶化ガラスの連続成形装置
JP2016525059A (ja) * 2013-07-16 2016-08-22 コーニング インコーポレイテッド 薄ガラスを曲げるための装置及び方法
KR102410492B1 (ko) * 2015-07-23 2022-06-20 삼성디스플레이 주식회사 글라스 성형 장치
CN105258645A (zh) * 2015-09-06 2016-01-20 苏州南光电子科技有限公司 基于激光和ccd的玻璃厚度测量系统
FR3050604B1 (fr) * 2016-04-25 2019-11-15 Eurokera S.N.C. Article vitroceramique
CN106587586A (zh) * 2016-12-22 2017-04-26 重庆天和玻璃有限公司 玻璃切断装置
TW201917340A (zh) * 2017-08-31 2019-05-01 美商康寧公司 改良式陶瓷輥床及測量方法
DE102018103661A1 (de) * 2018-02-19 2019-08-22 Schott Ag Transparenter Artikel aus Glaskeramik mit hoher Oberflächenqualität sowie Verfahren zu dessen Herstellung
WO2020018285A1 (en) 2018-07-16 2020-01-23 Corning Incorporated Methods of ceramming glass articles having improved warp
WO2020018408A1 (en) * 2018-07-16 2020-01-23 Corning Incorporated Methods for ceramming glass with nucleation and growth density and viscosity changes
KR102618611B1 (ko) 2018-07-16 2023-12-27 코닝 인코포레이티드 개선된 특성을 갖는 유리 세라믹 물품 및 이의 제조 방법
DE102018216743A1 (de) * 2018-09-28 2020-04-02 Schott Ag Arbeitsplatte insbesondere für Küchenmöbel, Kochtische oder dergleichen sowie Verfahren zur Herstellung einer Arbeitsplatte
CN111393028B (zh) * 2020-03-29 2022-09-06 重庆鑫景特种玻璃有限公司 一种具有局部增强结构的玻璃及其加工方法

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JP5595479B2 (ja) 2014-09-24
CN102378742A (zh) 2012-03-14
CN102378742B (zh) 2014-05-14
WO2010112148A1 (de) 2010-10-07
EP2414297A1 (de) 2012-02-08
JP2012521949A (ja) 2012-09-20
DE102009015089B4 (de) 2012-05-24
DE102009015089A1 (de) 2010-10-07
US20120094079A1 (en) 2012-04-19

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